This invention is generally directed to developer compositions, and more specifically, the present disclosure relates to developer compositions with coated carrier components, or coated carrier particles that can be prepared by, for example, dry powder processes, and wherein the coating is a polymer, or mixtures thereof containing a silicone resin or resins, such as TOSPEARL XC99-A8808™, TOSPEARL 105™ or TOSPEARL 120™, a silicone polymer available from GE Silicones, and wherein the TOSPEARL™ has been characterized as monodispersed particles of an alkyltrialkoxysilane hydrolyzed and condensed into spherical resin particles. TOSPEARL™ is believed to possess a network structure with siloxane bonds extending three-dimensionally, and wherein the silicon atoms can be bonded with one methyl group, in a structure intermediate between inorganic and organic, for example, of the formula wherein R is methyl
Alkyltrialkoxysilane can also be considered as a material wherein the alkyl prefix varies based on the number of carbon atoms in a continuous sequence bonded to the silicone atom, and also manufactured by Toshiba Silicone Company, a fine powder with a medium particle size diameter of from about 200 to about 3,000 nanometers, more specifically from about 300 to about 1,000 nanometers, and yet more specifically from about 400 to about 800 nanometers; and still more specifically about 500 nanometers, such as methylsilsesquioxane TOSPEARL XC99-A8808™. More specifically, the present disclosure relates to compositions, especially carrier compositions comprised of a core, and thereover at least one polymer, and dispersed therein and thereon a silicone polymer of a suitable average size as illustrated herein, such as from about 300 to about 2,000 nanometers, more specifically from about 400 to about 1,000 nanometers, and yet more specifically from about 500 to about 700 nanometers; carrier particles containing the silicone resins disclosed herein can impact triboelectric charge without affecting or minimizing carrier or developer conductivity, and wherein the nanometer size of the silicone polymer ensures that the silicone can be processed in a binder resin resulting in silicone beads becoming embedded in the fused polymer coating, such as polymethylmethacrylate (PMMA), firmly attaching the silicone particles to the carrier surface. Also, with the silicon resin or resins contained in the polymer coating there are enabled excellent developer triboelectric characteristics, and wherein in embodiments the carrier triboelectric charges can be adjusted to preselected values without adversely impacting other carrier properties, such as carrier conductivity, developer relative humidity sensitivity, and other functional properties.
In embodiments of the present disclosure, the carrier particles are comprised of a core with a coating thereover of a polymer, such as a polymethylmethacrylate (PMMA) and the like, including copolymers of methylmethacrylate and dimethylaminoethyl methacrylate, methylmethacrylate copolymers with substituted alkyl aminoethyl methacrylate, butylaminoethyl methacrylate, and the like, and which polymer coating contains a silicone polymer. The carrier may include the polymer coating thereover in admixture with other suitable polymers, and more specifically, with a second polymer, such as a fluoropolymer, polymethylmethacrylate, poly(urethane), especially a crosslinked polyurethane, such as a poly(urethane)polyester and the like, and moreover, the copolymer coating contains in place of a conductive component, such as carbon black, silicone polymer of nanometer size, and which silicone polymer component is dispersed in and on, or in the polymer coating. With the silicone polymer component, there can be enabled carriers with increased developer triboelectric response at relative humidities of from about 20 to about 90 percent, conductivity ranges that are unchanged in comparison to carriers without silicone particles in the carrier coating, and carrier conductivity ranges of from about 10−11 to about 10−6 (ohm-cm)−1. An advantage associated with the carriers of the present disclosure with the polymer coatings thereover include a decreased triboelectrical charge, for example, a carrier tribo of from about a plus (positive charge) 47 to about 60, or to about 53 microcoulombs per gram, and wherein decreased refers, for example, to from about 15 to about 25 microcoulombs per gram from the initial charge. Thus, when the initial carrier charge is about 50, this charge can be reduced to about 30 subsequent to the addition of the silicone resin. Carrier coating containing the silicone resin in amounts of from about 0.06 to about 0.5 percent by weight based on the weight percent of the total of the core, polymer coating and the silicone resin, had a triboelectric range of about 23 to about 47 microcoulombs per gram as determined by the known Faraday Cage method.
The carrier particles of the present disclosure can be selected for a number of different imaging systems and devices, such as xerographic copiers and printers, inclusive of high speed color xerographic systems, printers, digital systems, a combination of xerographic and digital systems, and wherein colored images with excellent and substantially no background deposits are achievable. Developer compositions comprised of the carrier particles illustrated herein and prepared, for example, by a dry coating process are generally useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes. Additionally, the invention developer compositions comprised of substantially conductive carrier particles are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected and then decreased, which charge is dependent, for example, on the polymer composition and dispersant component applied to the carrier core, and optionally the type and amount of the silicone resin selected.